Automatic telephone system



April 30, 1929. c. E. LOMAX 1,710,934

AUTOMATIC TELEPHONE SYSTEM Filed April 12. 1926 Ii'mTE'F-- Zarsnsa E.Lnmax Patented Apr. 39,

UNITED STATES PATENT our! CE.

CLARENCE E. LOIMAX 0 @AK PARK, ILLINOIS, .AESIGNOR, BYMESNEiASSIGNMENTS,

TO AUTOMATIC ELJZCTIHC ING, 0F GHIOAGQ;

WARE.

ILLINOIS, A CORPORATION "OF "DELA- AUTOMATIG TELEIIiONE SYSTEM.

Application. filed April 12,

This invention relates in general to auto .mutic tr-dephone systems inwhich connections are established through the medium of sub scrihercontrol ed automatic switches, but is more particularly concerned withsuch automatic telephtnie systems as include party lines and selectiverin in; equipment at the central exchange.

In any telephone system, in order to establish a talking connection witha particular party on a party line, some means must be provided tor sigrnalingr the particular party on the line with which a callingsubscriber wishes to coininunioatm and this pitt'erably withoutactuatiiur the bells at the other substations on the same line. llui'nerous methods of selectively gnali 11;; a particular party on aparty line have been proposed and are in use. The method in common useby the Bell Telephone Company tln-oiuighout the United States one whichdepends for this selective action on the use o't positive or negativeringing current impulses applied to either one or the other side of theline.

In the patent to Martin No. 1,52%h19d, an adaptation of this method toautomatic telephone systems is described. In this system, each pal yline is made accessible to the corn nectors of four different groups,the connectors of each group beingarranged tosupply ringing currentimpulses ot a certain kind over a re]. iin side of the line to signal aceu tain one of tour parties on the line. This systemr whilesatisfactory from an operating point of View, requires the use otmoreconnector switches per one hundred lines than would be necessary if allthe connectors having access to the one hundred lines were in one largegroup.

The principal object of the present invention is the provision of a newand improved connector switch having an individual means for selectinthe kind of ringing current i1npulses and the side of the line to whichthey are to be applied, for particular use in a full selectivetour-party line telephone system in which "full selection is obtained bythe application of either positive or negative currentimpulses to one orthe other side of theline By the utilization of this new and improredconnector switch in the above described systom, the number of connectorsneeded for a certain number of party lines will be considerably lessthan are necessary when the party 1826 Serial No. 1013234.

lines are accessible to the connectors ofitour ditterent groups.

The invention, its object and other features a not specificallymentioned, will be desci'ibcd in detail hereinafter, reterenee beingihad:to"

the acc-olnpanyiirg drawing, in which is shown eutlicicnt ot theapparatus in an automatic telephone system to enable the inventionto beexplained and understood.

The reference character-A indicates an automatic substation of the usualtype, which ot the well knownrotary type whose wipers have no normalposition and move in aforward direction only. Asis well knownhthefunction of the individual line-switch'is to extend its associated lineto anidle selector switch when the receiver is raised at the substationto initiate acall.

One oi the first selector switchcs, to which the line switch C hasaccess in common with other similar line switches, is indicated in thedrawing by the rectangle D. Inasmuch as selector switches are wellknownin the art, it has not been considered necessary to show thecircuits in detail. It may bestated briefly that the selectorD is aSt-row ger Vertical and rotary switch ofwell known mechan= icalconstruction, and operable according: to the two-wire system of control.Then used in setting up a connection in the system as shownin thedrawing, the selector responds to the first digit in the called numberinorder to select a desired group of connectors, after t which theselector automatically rotates to selectand connect with a trunk lineextending to an idle connector in theselected group The above is, ofcourse true only of a one thousand line system; if the capacity ofethesystem grcaterthan this, second or third selectors Will be interposedbetween the first selectors and connectors in the well under- This is inaccord with the.

stood manner. usual percentage trunking system, however, and neednot bediscussed in detail.

One of the trunk lines to which-theselectm' D has access is shown in thedrawing as extending tothe connector E which is also a Strowger verticaland rotary switch having a capacity of one hundred subscribers lines.The connector E is operable according to the two-wire system ofcont-roll similar to the selector D, and responds to the next two dig-its in :1 called number to complete the connection to the called line.

One of the party lines to which connector E has access comprises lineconductors lit :uid 1 152 to which the substations A to it; elusive areconnected. These substations are of the well. known type used in theabove de scribed type of full selective party line systom, thesubstation A being shown in full and only the ringing circuits ofsubstations A i and A being shown. The line switch C is associated withthis party line at the central exchange and is similar to line switch C.

Just below the connector E, the auxiliary switch ll is shown which isindividual to the connector E. This switch, comprising; the wipers 122and 123 and their associated sets o t ljianks, the stepping magnet 120,and the re lease uiagent- I121, constitutes with its controllingcircuits the means above referred to which predete 'inines the hind o'tringing current impulses and the side ot the line to which they are tobe applied for signalling a particular subscriber on a party line.Switch l? perit'torins this function responsive to the dialinn ot thelast digit in the called number.

The common ringing equipment for pro ducing positive pulsating currentand negative pulsation current comprises the it. C. genera-tor G, thethree additional batteries B B and B, and the interrupter I, the batteryll being the regular exchange battery. With the connections as shown,positive pulsations are inter nittentl'y impressed on conductor 1-432and negative pulsations are intermittentl v impressed on conductor 14:1.'1." he battery 13' and the exehi'inge ljiuttery l3 serve as trio pingbatteries for operating the ring, cut-ott relay in the connector when asubscriber answers a call during the silent period.

With this general description of the system and the apparatus used inmind, a further iniderstanding j of the invention may be gained from adetailed description of the ope. ations which take place when onsubscriber another subscriber on a party line. For this purpose it willbe assun'ied tl at the subscribe. at substation A desires to establish aconnccti on with asubscriber at substation lid. l'Vhen the receiver isremoved at the calling station, a ciraiit is completed over the conductors' ll and 12 for the slow acting line relay 15. Upon energizing,relay 15 closes a circuit at armature 20, which includes the winding ofthe switching relay let and the stepping magnet 16 in series; and at itsarmature 21 connects the test wiper 26 to the above circuit at a pointmidway between the said switching; relay and the magnet. The op erationnow depends upon whether the trunk I) are now enernir line with whicothe line inviteh wipers are asseciated is busy, or is not bur-w. lt thetrunk line is busy, there will be a round potential upon the testcontact wit which the test la); i will he she h and the step "I i reshort circuit is removed from '.i rel v and the operation ot i toppii'iiagrnet it; will cease bi ause ot the high resiiaatance ol': the saidswitching re luv. llhe latter relay however, is energ'ixed and groundsthe test wiper at its armature i8, and at it. arnutturrs l? and itdisconnects the line ctmdimtors ti and 12 from the winding of the linerela v l5 and 'tl'Olll around. rcspeetivel v, and extends them by: wayot wipers E35 and and haul: contra-ts Q9 and 30 to the line relay (notshown) of the first selector l). The line and release relays ot theselector in the usual manner and the latter rela' ground :the rel usetrunk conductor ot the trunl: lii e n order to establish a holdingcircuit tor the rwsiteliiusi relav ll of the line switch (3. Thisoperation is well understood and need not he explained turther. A

The calling: subscriber nia'v now operate his calli g); diwice inaccordance with the first digit in the desired iuunher. lu response tothe interruptions in the line thus produced. the Yerlical magnet oi theselector D is on eratetl under control of the line relay to raise thewipers ll) "h inclesivc. to the particular level in. which a c trininated the trunlt lines extending to the desired group of connec rswitches Thereafter the rotary or trunk so lect movement initiatedauto:naticallt in the usual manner. and the wipers are retated in searchof an idle trunk line. Arsune i n 51' the i the trunk line shown in thedrawino; 1st l( l'trSt idle trunk line, then when the vipers arrive tthe test wiper i l. will find no ground potential upon the lost contactall, and the rotation of the switch will cease lVhen this occurs. theincoming line coi'idurtors are extended in the usual in oer by way oithe switch wipers l0 and i2 bank contents t?- und 4-5. and contactsprings CUl'lil'Olltitl by the revershu relay 50 to toe wind s of thedouble wound ielajv 51 ot the co: ctor l Vt hen the line i1: extended .2s above o'escrihed, the line rent} iii is energized over the linecircuit to close a circuit tor the slow-acting release relay F llpouenergizing. relav prepare-1 a circuit. tor i he vertical lilttt? not 58at its armature (3'2", and at its armature it bank contacts 413-45inclusive magnet 58 to battery.

tary magnet 59 to battery.

65 connects ground. to the release trunk conductor 47, therebycompleting a holding circuit for the selector D and the line switch l inthe well known manner. The walling subscriber only now operate hiscalling device in am-ordance with the next digit in the desired number.As a result, the line relay 5.! is deenergineifla plurality of times,andat the first deenernizcation transmits a current impulse to thevertical magnet 53 over the following circuit: grounded armature (it.and its resting contact, armature UT and its working contact, olinormalsprings (3i and 63, winding; of the slow to release series relay 53, andthe winding of the vertical By the operation of the vertical magnet, thewipers 90-"92, inclusive, are raised step by stop until they standopposite the level in which is terminated the line to substation A Theslow to release series relay is energized in series with the verticalmagnet and by means of its armature (3R maintains the circuit of thevertical nougnet intact after the otl' normal springs have been shifted,which occurs on the first vertical step. At the end of the verticalmovement of the switch, relay 53 is deenernized and transfers theoperating circuit to the rotary magnet 59. r l

The subscriber will now operate his call inn device in accordance withthe next digit of the desired number, which is the last digit which hasto do with the line selection. ll hen the calling device is operated,the line relay 51 responds as before and sends impulses to the rotarymagnet 59 over the fol l()\\'lI1f) circuit: grounded armature (ill andits resting contact, armature 6'7 and its workin contact, off normalsprings 61 and G2, armature 68 and its resting contact, resting; contactand armature 75, armature S5 and its resting contact, and the windingofthe ro- By the operation oi? the rotary magzjiict, the wipers 90-92,inclusive, are rotated step by step and are finally brought to rest inengagement with the bank contacts in which the line to substation ittrrminates, these bank contacts being indica l in the drawing hv thereference chars 93, 9t and 95. The slow to release rclay an is energizedin multiple with the rotary magnet and retains its armature attractedthroughout the rotary movement of the switch. At its armature 78, relay.56 connects thotest wiper 91 with the test relay and at its armature T9the said relay 536 ch a a shunt around the contact at armarnre 75 ot thetest relay. The latter operat ion is to prevent the test relay fromonenin the rotarymznrnet circuit while the test wiper passing overliiusy test contacts.

It be assumed first that the railed line iv; busy Such being the case,when the test wiper 91L arrives at test contact 94, it will lind a groand potent-ialthereon, the test relay will be energized, and whenitheslmv to release relay 56 dcenergizes at the end (if the rotary movementof the switch, the test relay 5 establishes a locking circuit/for itselfat its armature Tel. lelay 55 also opens the rotary magnet circuit atits armature 75, thus rendering the impulse circuit incllective at thistime in case the calling subscriber dials the last or ringing currentselecting; digit. ltclay also at its armature 77, connects a lead fromthe bus? signaling machine BM in the lower heavy talking UOIltlllCtOl'.By this latter operation, an audible signal is transmitted to thecallingsubscriber, and, being; advised thereby that the called lineisinaccessible for the time-being, he will hang up his receiver.

lllaving explained the operations which take place when the alled lineis busy, it will now be assumed that theline is idle when called. Underthese circumstances, when the test wiper 91 arrives attest contact 94,it will find no ground potentialand the test relay :35 will not beenergized. Then when the slow to rcloaserelay56 deenergizcs at the endof the rotary movement of the switch, a circuit is completed for theslow acting switching relay as .:tollows: From the grounded releasetrunk conductor l? by way otarniature H and its resting contact, upperwinding" of the switehingrelay 57, resting contact and armature 8, testwiper Slytest contact 9%, winding o'l'hthe s-witchi ng'relay ll-l,:l11tlthe whaling of the stepping magnet 1th to battery. Relaysfi? andli-luare energized in series over the above circuit,- and the latterrelay is operated toclcar the calledlinc of its normal. battery and ground connections in the line switch G It should be noted that the relayill is not fully operated at this time, due to a Illl0(3l1:llll-3tll.llltfll'lutiklllg arrangement between the[armature of thisreluy andthe armature or the slow acting line. relay (11:5, and thewipers ot' theline switch 0 are not connected. up. 111 the connector E,switching;- relay 5?, in. energizing, establishes. a locking; circuitfor itself at its armature til, grounds the test wipertll at armature83,

transfers the lllllflllbfll'lll' circuit from magnet 59 to the steppingmagnet. hill of the ringing current electing switch F at its armature85. and prepares a circuit at its armature 86 l which provid fortransmittingr a tone signal to the calling subscriber during the ringingoperation, i

The calling subscriber may now operate his calling device in accordancewith the.itina1 digit in the ninnber, "which is the digit whichdetermines the proper ringing current and the side of line to which itis to be implied for signalling the particular station wanted. Thesubstations A iV, inclusive, have been nnmbe red tor convenience in.accordancewith the digits to which. they correspond, and'since thesubstation A is the Wanted substation in i the present case, the finaldigit to be called will be the digit 4. lVhen the calling device isoperated for this digit, the line relay 51 transmits four impulses ofcurrent to the step ping magnet 120 of the switch over the followingcircuit: From grounded armature (ll and its resting contact, armature(i7 and its working contact, oft normal springs 61 and (i2, armature (l8and its resting contact, restin g contact and armature 7 armature 8:)and its working contact, and the windings of the stepping magnet 120 tobattery. By the operation of magnet 120, wipers 122 and 123 are given astep by step movement and are finally brought to rest in engagement withthe fourth contacts in their respective banks. The slow to release relay56 is energized in multiple with the magnet 120 and now serves toprevent the energiaation of relay 55 by holding open its energizingcircuit at armature 8( which circuit will he explained. hereinafter.

With wipers 122 and 123 in engagement with the fourth contacts of theirrespective banks, a circuit for the signal control relays 131 and 132 isclosed which may be traced from ground by way of armature 66 and theworking contact, wiper 122 in engagement with a fourth bank contact,through the winding of relay 131 to battery; and from ground by way ofarmature 66 and the working contact, wiper 123 in engagement with itsfourth hank contact, through the winding of relay l to battery. Bothrelays 181 and 132 are energized and perform the following circuitchanges: At armature 133 and the working contact, the common ringingconductor 142 connected to the upper terminal of the upper winding ofthe ring cut-oil relay 1. The lower terminal of the upper winding ofring cut-oil relay 54 is connected by way 01' armature 134i and theworking contact and armature 136 and the working contact to the ringingconductor 14.4. At armature 135 and the working contact, groundpotentialis connected to the conductor 143. These operations prepare thesignalling circuit, predeterniining the kind of signalling current andthe side of the line to which it is to he applied.

At the end of the series of impulses transmitted to magnet 120, relay 56is deenergized and completes the circuit for relay 55 as follows: groundby way of springs 124 which close on the first rotary step of theselector switch F, resting contact and armature 80, through the windingof relay 55, which now functions as a ringing circuit control reh y, tobattery. Relay 55 now energizes and performs the following circuitchanges: At armature 77 a circuit is closed for the ring back tone whichmay be traced. from conductor 96 connected to the ring back tone source,work ing contact and armature 86, working contact and armature 77,normally closed springs controlled by armature 71, to the lower heavytalking conductor. By this means a ring back tone is transmitted to thecalling subscriber to apprise him that the alled subscriber is beingsignalled. At armature T3 the circuit for the release magnet 121 of theswitch F is prepared. At armature 75 the impulsing circuit is openedthereby making any further manipulation of the dial. at the callingsubstation ineffective. At aruiaturcs T2 and 76 the signalling circuitis con'ipletcd which may be traced as follows: from common ringingconductor 142, to which positive ringing current impulses and positivebattery are alternately connected, working contact and armature 183, theupper winding of the ring cutoff relay o1, armature ll-l-l: and theworking contact, armature 136 and the working contact, conductor 111-,working contact and armature '76, resting contact and armature 71,armature 87 and the working contact, wiper 92, bank contact 95, lineconductor 112 through the winding of the A. C. relay 103 at substationit to ground, and through the winding of the A. C. relay lthl at thesubstation A to ground. Due to the condensers in series with the A. C.relays at the ruxhstations, alternating currents are set up in the twoA. C. relays 103 and st. Responsive thereto, these relays operate andvconnect the ringers st and 153 directly across the line conductors. Assoon as these ringers are connected across the line, pulsating currentwill pass through the two ringers over the above traced circuit fromconductor 11.2, and by way of the armatu res of the A. (l. relays andtheir working contacts, line conductor 111, hank contact 93, wiper 90,working contact and armature 81, armature 69 and resting contact,armature 72 and the working contact, ringing conductor 14-3, workingcontact and armature 135 to ground. The ringers at the substations arebiased in the ordinary way. Ringer 155, is adapted to respond only tonegative pulsating current, while ringer rat is zulaptcd to respond onlyto positive pulsating current. It follows therefore that since theciurront is being supplied from the positive pulsating ringing conductor1412 only the ringer 15 1 will respond. I

In this manner the :uibscriher at substation A is selectively sigiiialeduntil he answers the call or until the calling subscriber replacrs hisreceiver. It may be mentioned at this time that the ring cut-oft relay51 adjusted that it will not operate responsive to the ringing currentimpulses or to the current supplied from the tripping battery B duringthe silent period, the current in both instances being limited by thecomparatively high resistances at the substations.

lVhcn the subscribers at substation A removes his receiver to answer thecall, howc ver, a low resistance bridge placed across the lineconductors including the transmitter and the primary winding of theinduction coil at the called substation. The flow of current lltl it t)in the circuit including the two line conductors in series is therebysulliciently increased to cause the instant operation of the ringcut-oil relay 54, this current being either from the battery it in.series with generator durii'igthe silent period. Upon energizing, whyolcloses the locking circuit for itself at.

armature To, and atarmatures 69 and 71 and their working contacts thetalking connection. :tronrthe substation A to the substation A isfinally completed, the signaling circuit being-opened at the restingcontacts of these arinatures. The ring back tone circuit is also o pvnedby the separation oi the normally closed springs controlled by armature71. As soon as the talking connection is completed to the called line,the back bridge relay 50 operates over the called line loop andperioruisthe usual operation": of reversing the battery connections to thecalling line. This latter operation is of no utility in connectionwithlhe apparatus shown, but is the standard operation for use incontrolling measured service equipment when such equipment is suppliedand is therefore included.

Uoni'ersation may now proceed as desired, and when the subscribers arethrough they willboth replace their receivers. Replacing the receiver atthe called substation merely causes the deenergization oi. the backbridge relay 50 which thereupon restores its arnialures to normal. Inresponse to the replacenuuit ol the receiver at the calling substation,the line relay 51 deenergizes after which the release relay 52 isdeenergized. In deenergiaing, relay V 2 initiates the release of theentire conncctionin the usual manner. By the restoration ol' armature 65ground is removed :l'roni the release conductor 4:7, thereby permittingthe selector D and line switch to restore to normal in the usual manner.In addition thereto, the circuit tor the release relay 121 of the switchF is closed which may be traced from ground by way of armature U andresting contact, armature 73 and the working contact, through thewinding of the release magnet 121 to battery. Release magnet 121operates and restores the wipers 122 and 123 of the switch F to normal.The release of armature 66 opens the circuit of relays 131 and 132, andswitching relay 57, which. likewiserestor-c to normal. By the releaseaoiarmature 64: and armature 67, the

usual circuit for the release magnet is glass: and restores itsarinatures to normal.

All the apparatus used in the establishment of the connection is thusfreed and may be used in the establishmentot' another connec tion.

an explanation will now be givenof the nlannerin which a connection withthe other three stations on the party line may be establishcd. Thesubstations A A, and A may be reached by dialing the same party linenumberand by dialing the digits 1,2 and 3, respectively, as finaldigits. Theoperations performed in establishing a connection with anyone of the other three substations are exactly the same as whenestablishing a connection to the substation A, with the exception of theoperations of relays 131 and 132 which controls the polarity of thepulsatingsignals ing current and the line conductor to which it isapplied, which in turn predeterniines which ot the tour ringers is tooperate. Should a callingsubscriber desire to converse with thesubscriber at substation Aihe will dialthe same line number and thendialthe digit 3 as the linal digit; In response toudialingthe line number,the selector D and the connector lfi, assuming thatthese switches areagain taken for use, operate in the manner described above. In responseto the dialing of the linal digit 3, wipers 122 and 123 01 the switch Fare positioned on the third set of contacts-in their respective banks.In this case no circuit is closed for the rela' 131 but a circuit is aain,

lhe common ringing closed for relay 132. conductor 141 then remainsconnected to the lower terminal of the upper windingof relay 5st. Groundis again connectedto the ring-. ing. conductor 1&4: at armature 135 andthe working contact, and the upper terminal of. the. upper winding ctrelay 5a is connected to ringing conductor 14i4 by way of armature 133and the resting contact and armature 136 and the working contact. Thesignalingcircuit is identical to thattraced for signaling the subscriberat substation At, except that negative pulsating current fromthe commonringing current conductor 141 instead of positive pul eating. currentfrom conductor 142 is used. Both relays 10 l and 103at the substations 21V and A operate as before. Ringerlfid will not respondto negativepulsations. Ringer is adapted to respond to negative current impulsesand therefore operates whenever it IS br dged across the line byoperation of relay 103, thereby signalingithesubscriber at sub station ATo signal the subscriber at substation A, the

final digit to be dialed is the digit In this spective banks. In thiscase, relay131 open ates and relay. 13. remains deenergized. Ground isnow connected to conductor 144 by way of armature =and therestingcontacta andpositivecurrent impulsesare suppliedfrom.conductor3'1l2 by way ofthe Working contact and lllilfitltllil-l133 through the upper winding of relay 54:, armature 134; and theworking contact, armature 136 and the resting contact, conductor 1-1 3,from where the circuit extends by way of working contact and armature72, resting contact and armature (it), armature 81 and the workingcontact, wiper 90, bank contact 93, line conductor 111, through the A.C. relay 102 at substation A and the A. C. relay 101 at substation A inparallel to ground. Relays 102 and 101 operate responsive to thesignaling current impulses in the same manner as did relay 10a and 103.The ringer 152 is biased the same as ringer 15%, and ringer 151 isbiased the same asringer 152- Ringer 152 therefore operates responsiveto the positive current impulses when connected across the linecoi'iductors to signal the subscriber at sulistation A.

To signal the subscriber at substation A the final digit to be dialed isthe digit 1. in response to the dialing of the digit 1, tlfftfil theline number is dialed, the wipers 12:2 and 1225 are positioned on thehrst contiwt in their respective banks. Neither relay 1251 nor relay 132is operated in this case. 'lhe signaling circuit is the same as that forsi ding the si'ibscriber at sulistation A except tiat negative currentimpulses are now supplied from the conunon conductor 1 5-1, to which theringer 152 is not responsive, and to which the ri uger 151 responds tosignal the subscriber at uhstation A it is evident from the drawing andthe above description that relay 131 performs the function oi selectingthe source of ringing current and. that relay 132 ,)erforn1s the tunetion of dcterniining to Which side of the line the selected source ofringing current is to be Connected. Relay 131 also reverses theconi'iections to the upper winding of relay 54 when the ringing currentfrom conductor i i-i3 is selected. Inso doing, the current flow throughthe upper winding of relay 5 1 is made to flow in one directionregardless of whether positive current impulses or nega tive currentimpulses are used, this being the same as the direction of current flowin the lower winding of relay F4: when the circuitot the lower windingis closed at armature "70. Such a provision is obviously necessary forthe satisfactory operation of the cut-oil relay 54. i

This completes the description of the operation of the new and improvedconnector switch and its features. What is considered new and desired tohave protected by Letters Patent will be specifically stated in theappended claims.

\Vhat is claimed is:

1. In a party line system, a connector switch for extending calls from acalling line to a called party line, sources oi positive and negathsignalling current, a signalling cincuit, aria-oil relay in said switchadapted tor said cut-0113' relay in said signalling circuit so that thedirection oi current through the winding oit said cut-oll' relay is thesame re;

gardless ot the source selected.

2. In a party line system, a connector switch for extendin calls ironi acalling line to a called party e sources (it positive and negative si 5current, a signalling circuit, a cut-oli relay in said. switch adaptedfor inclusion in so id circuit and operative res ponsive to theanswering ot a call by a called subscribcr to interrupt said signallingcircuit, means in said. switch 'i'or controlling the solect-ion oil? thesource elf signalling current and or controlling the cinincctions ofsaid cutoil relay in said :--i' na.lling circuit so that the directionoi curre .t through the winding of said cut-oli re iy is the sameregardless oi. the source selei u, and means in said switch fordetermining the side 01 the line to which the selected source isconnected.

pin y line system, a connector ing calls from a calling line l. pa. tyline, sources o'l positive and negative signalling current, a signallingcircuit, a cut-oil relay in said switch adapted for inclusion in said.circuit and operative rcsponsive lo the answering of a call by a calledsubscriber to interrupt said signallingcircuit, means in said switch forcinitrolling the sclection ot the source oil signalling current and forcontrolling the connections oi. said cutoil relay in said signallingcircuitso that the direc ion oi our out through the winding o'l" saidcut-oil relay is he same regardless oi" the source selected, means fordetermining the side or the line to which. the selei'ited source isconnected, and means individual to said connector tor controlling bothsaid first and said second means.

i. in a telephone gsleui, a party line, sources oi positive and negativesignalling current, a connector -awitch, means for operating saidconnector to connect with said line, means in said connector directivelycontrolled. over a calling line for connecting either of said sources tosaid line to selectively signal stations on said line, a cut-oil relayin said connector having a winding adapted for inclusion in thesignalling circuit and having a locking winding, and circuitarrangements such that both windings of said cut-oil relay cooperatewl'icn said relay is operated regardless oi the source of signallingcurrent used. 7

5. In a telephone system, a party line, sources 01' positive andnegativesignalling current, a connector switch, means for operating saidconnector to connect with said line, means in said connector forconnecting either of said sources to either side of said line toselectively signal stations on said line, .a cut-oil relay in saidconnector having a wind- :ing adapted for inclusion in the signallingcircuit and having a locking winding, and circuit arrangements such thatboth windings of said cut-oil relay cooperate when said relay isoperated regardless of the source of signalling current used.

6. In a party line connector, means for operating the connector inaccordance with a digit of a desired telephone number to select adesired line, a ring cut-oflrelay, a source of positive ringing current,a source o'l negative ringing current, means operative in accordancewith a dillerent digit of the telephone number to select one or theother of the sources of ringing current and connect it to the selectedline in series with the ring cutoff relay, and commutating means formaintaining the direction of flow oi current tl'irough the relay thesame regardless of the source used.

7. In a party line connector having a pair of line wipers, means foroperating the connector in accordance with a dig ot a desired telephonenun'ilier to select a desired. line, a ring cut-oil relay, a source ofpositive ringing current, a source of negative ringing current, meansoperative in accordance with a different digit of the telephone numberto select one or the other of the sources o'l. ringing current andconnect it to one or the other of the line wipers in series with thering cutoff relay, and commutating means for maintaining the directionof flow of current through the relay the same riigardless oi" the sourceused.

8. In a party line COIHIQCtOl, means for operating the connector inaccordance with a digit of a desired telephone numher to select adesired line, a ring cut-oil" relay having an operating winding and aholding winding, a source of positive ringing current, a source ofnegative ringing current, means operative in accordance with a differentdigit of the telephone number to select one or the other of the sourcesof ringing current and connect it to the selected line in series withthe operating winding of the ring cut-oil relay, and cominutating meansfor maintaining the direction of flow of current through both windingsof the cut-off relay the same regardless of the source of ringingcurrent used.

9. An automatic telephone system wherein a connector is operative inaccordance with value of certain digits in a party line telephonenulnher to select the line and wherein means is operative in accordancewith a diflierent digit of the number to select a source of ringingcurrent to ring the desiredstation on the line, and wherein a cut-offrelay having two windings has one of its windings included in theringing circuit and is operated over that winding when the called partyanswers and 1s locked in its operated pos1- tion over the secondWinding, characterized in this, that the ringing current to be select edis either positive or negative current, and connnutating means isprovided for main taining the relative direction of the current flowinthe two windings the same regardless oi the source of ringing currentused. I

1.0. An automatictelephone system where-' in a connector having two linewipers is op: crative in accordance with the value of certaindigits in aparty line to select the line and wherein there is means operative inaccordance with the value of a different digit in the number to selectone of two sources ()fl' ringing current and to connect the ring lockedin its operated position over the sect 011d winding, characterized inthis, that the r1ng1ng current to be selected is either posithe ornegative current, and connnutating.

means is provided for inaintainingthe relative direction of the currentflow in the two windings the same regardless ot'the source oiiringingcurrent used. a

In witness whereof, I hereunto subscribe 7.

my name this 8th day of April, A. 1)., 1926.

CLARENCE n. LOMAX.

